Whey is useful in all of its forms. In some cases whey is processed to directly recover whey protein and leaves behind a material often referred to as deproteinized whey, which refers to the liquid remaining after treatment of whey to remove the majority of the whey protein. The material is not deproteinized completely, but contains most of the insoluble membrane protein fragments from milk fat globular membrane (MFGM) originally present in the whey. When produced by some procedures, the fat content is essentially removed. In others, such as ion exchange chromatography, the fat is not removed and is carried along with the deproteinized whey and contains proteins associated with the fat. This fraction contains most of the insoluble membrane fragments. Deproteinized whey is manufactured through the ultrafiltration of sweet dairy whey, removing a portion of the protein from sweet whey to result in off color viscous fluid containing greater than 80% carbohydrate (lactose) levels. Traditionally lactose is hydrolyzed to equimolar mixture of d-glucose and d-galactose by enzyme lactase or using mineral acids such as dilute hydrochloric acid.

Typical quality of commercially available deproteinized whey has composition shown in Table 1.
TABLE 1TYPICAL COMMERCIALLY QUALITYDEPROTEINIZED WHEYAnalysisSpecificationTypical rangeTest MethodMoisture (%)5.0 max.4.7 +/− 0.2Karl FisherTotal Protein5.5 min. 7.5 +/− 1.0Leco Combustion(%)Fat (%)1.5 max.0.9 +/− 0.3MojonnierAsh (%)11.0 max. 10.0 +/− 0.4 Residue onIgnitionLactose (%)74.5-81.577.5 +/− 1.5 By DifferencepH5.8-6.56.1 +/− 0.110% Sol. @ 20° C.Scorched15 mg/25 g max.7.5 mgADPIParticles
D-tagatose can be formed from d-galactose by enzymatic isomerization. Typically, the isomerization is carried out in the presence of L-arabinose isomerase under alkaline conditions in the presence of calcium. D-tagatose is useful as a food additive, as a sweetener, as a texturizer, as a stabilizer, or as a humectant. D-tagatose is also useful in formulating dietetic foods with a low glycemic index. Potential applications of d-tagatose include breakfast cereals, diet soft drinks, reduced fat ice cream, hard and soft candies, chewing gums, dietary supplements, and special diet food for meal replacement.
A variety of methods exist for separating polar organic substances from ionic substances. Many of these methods require multiple purification steps and do not achieve complete separation. For example, U.S. Pat. Nos. 5,968,362 and 6,391,204 describe methods involving the use of an anionic exchange resin to remove heavy metals and acid from organic substances. However, these methods are not amenable to complete acid removal, nor do they allow for removal of inorganic and organic cations and anions simultaneously. Similarly, U.S. Pat. Nos. 5,538,637 and 5,547,817 describe methods for separating acids from sugar molecules. However, these methods are limited to separating acids and are not applied to the simultaneous removal of all forms of inorganic and organic cations and anions. Additionally, U.S. Patent Publication Nos. 2009100556707 and 200810041366 disclose using an ion exchange resin for separating first calcium sulfate then acids from sugar mixtures.
D-tagatose is typically produced in a two-step process wherein lactose is enzymatically hydrolyzed to d-Galactose and d-glucose using immobilized lactase. The d-galactose is typically separated using a cation exchange resin. The separated d-galactose is then isomerized to produce d-tagatose under alkaline conditions (typically at a pH of 12) using calcium hydroxide to form a precipitate. The precipitate is subsequently treated with sulfuric acid to free the d-tagatose, and the filtrate is demineralized in a cation and anion exchanger. Typically, the resulting solution is concentrated and purified by chromatic fractionation using a cation exchanger. The d-tagatose is recovered by crystallization.
Simulation of a moving sorbent bed is described in U.S. Pat. No. 2,985,589 (Broughton et al.), which is mentioned above. In accomplishing this simulation, it is necessary to connect a feed stream to a series of beds in sequence, first to bed no. 1, then to bed no. 2, and so forth for numerous beds, the number of beds often being between 12 and 24. These beds may be considered to be portions of a single large bed whose movement is simulated. Each time the feed stream destination is changed, it is also necessary to change the destinations (or origins) of at least three other streams, which may be streams entering the beds, such as the feed stream, or leaving the beds. The moving bed simulation may be imply described as dividing the bed into series of fixed beds and moving the points of introducing and withdrawing liquid streams past the series of fixed beds instead of moving the beds past the introduction and withdrawal points. A rotary valve used in the Broughton process may be described as accomplishing the simultaneous interconnection of two separate groups of conduits.
U.S. Pat. No. 4,412,866 describes an example of the operation of chromatographic simulated moving bed (or sometimes called “SMB”) method to separate the components of a feed stock. A resin bed is divided into a series of discrete vessels, each of which functions as a zone within a circulation loop. A manifold system connects the vessels and directs, in appropriate sequence to (or from) each vessel, each of the four media accommodated by the process. Those media are generally referred to as feed stock, eluent, extract and raffinate, respectively. As applied to a sugar factory, a typical feed stock is a lower purity sucrose solution, the eluent is water, the extract is an aqueous solution of sucrose and the raffinate is an aqueous solution containing non-sucrose, such as salts and high molecular weight compounds. The simulated moving bed disclosed by the '866 patent is of the type sometimes referred to as a “continuous SMB.”
An example of a batch chromatographic method for the purification of sucrose is described in the disclosure of U.S. Pat. No. 4,359,430, which utilizes sucrose, feed stocks derived from sugar beets at purities of approximately 7% to 60% sucrose. See also, e.g., U.S. Pat. No. 5,466,294, which utilizes a “soft raw syrup” as a feedstock to a chromatographic method which is not in a high purity form at a less than 89% purity sucrose on a dry solids basis, i.e., approximately 11% non-sucrose impurities.
U.S. Pat. No. 6,057,135 discloses a method of producing d-tagatose from lactose hydrolysate, comprising glucose and d-galactose. The method comprises subjecting the lactose hydrolysate to fermentation conditions whereby the glucose is selectively fermented to ethanol. The remaining d-galactose is separated from the ethanol to provide a solution having a concentration of from about 10% to about 60% by weight d-galactose. The solution of d-galactose is subjected to enzymatic isomerization with L-arabinose isomerase at an isomerization pH from about 5.5 to about 7.0 and a temperature from about 50° C. to about 70° C. The resulting yield of d-tagatose is from about 20% to about 45% by weight based on d-galactose.
Methods are sought to simultaneously produce high purity tagatose and an enriched glucose product using a combination of galactose isomerization and continuous chromatography or simulated moving bed separation.